How do I create this crease effect on glass?
I'm sure there are other solutions but i came to an very fast result with the help of the Screw Modifier.


click for flowerpower (Margarita by INFAMEDAVID)

The advantage of this modifier is that you can build your mesh with the desired angle of the Edge Loops which makes it a lot easier to model the creases.



Model


add a circle Shift+A
add the Screw Modifier

I used following settings:



You can use Z for wireframe to see the result





apply the Screw Modifier
add a Solidify and a Subdivision Surface Modifier
bring the object into the shape






Like you mentioned in your Question I also used a combination of Checker Deselect, selecting Edge Rings and Edge Loops to get the desired Selection and scaling it on the X and Y Axis.

S then Shift+Z





Node-Setup


I used this Glass Shader Setup from here





If you like to edit your existing model:

You can use Propotional Editing O


to rotate R your mesh around the Z-Axis
to scale S on X and Y axis to create the creases



You control the size of Propotional Editing with the Mousewheel


For more Information how to get every Nth Selection you can have a look here:


How can I select every Nth edge in only one direction on a plane?
Select every other face loop